For Gordon Ramsay, the past few weeks have been like living in his very own Kitchen Nightmare. Only it has extended beyond his kitchen and into every other room of his house. Like an unwatched pot, the TV chef's personal and professional life has boiled over in spectacular fashion, leaving the mother of all cleaning-up jobs.

Not that anyone is rushing to pull on the Marigolds; quite the contrary. In typical fashion, Ramsay has heaped more coals this weekend on to a fire he lit three weeks ago when he sacked his father-in-law, Chris Hutcheson. Specifically, he claimed his wife Tana has much to learn about what her father gets up to when not running restaurants, lashing out after his wife's parents wrote to their daughter, urging her to dump the man she married 14 years ago, aged 22.

The father of four was in combative form last week. Barely days after claiming he wouldn't be talking to the press about the farce enveloping his globe-spanning business empire, Gordon Ramsay Holdings (GRH), the chef penned an extraordinary open letter to his mother-in-law, Greta Hutcheson. He used it to heap innuendo on her husband's "complex" private life that left "many of my key staff feeling they have had to cover on his behalf". Ramsay, 44, who admitted hiring a private detective to follow Mr Hutcheson, added: "His away days were rarely what I thought they were." As if the insinuations weren't character assassination enough, Ramsay went on to denounce Hutcheson as a "manipulating and controlling... dictator". He also asked Mrs Hutcheson to stop "punishing" her daughter.

The letter should have been Ramsay's final word on the subject of his unravelling extended family. It wasn't. In a separate interview, he laboured the point about Mr Hutcheson's "away days", which he said "were becoming more of a permanent fixture" as his "excuses for disappearing" wore thinner and thinner. "'Where is Chris?' I would ask and be told he was in Paris for three days, sorting out the restaurant. Funny, I would think. We have already done that. Then I would ring up Paris and say, 'Can I speak to Chris? I hear he is there for the weekend.' Only to be told that Chris hadn't been there for six months."

To hammer home the point, Ramsay described how he'd been filling Tana, 37, in on the man she calls Dad. "She is getting up to speed – and that is a little scary. She knows about 90 per cent. She has been shocked. She struggled. It is a big blow. She had this perfect image of her daddy and it is not there," he said.

As one former acquaintance of Ramsay put it yesterday: "It's that 10 per cent that's dynamite."

It isn't just Tana's father who has been in Ramsay's line of fire. Her brother, Adam, formerly the managing director of GRH, was suspended and Adam's son Christopher sacked on the same day that Chris Hutcheson was let go. Ramsay may have spent 12 years building his business empire with his in-laws, but he needed barely 12 hours to go it alone.

Since losing his job, Mr Hutcheson, 62, has been busier than ever. As well as giving his own extensive interview, claiming to know where Ramsay's "bodies are buried" and calling his son-in-law an egotistical "monster", he has taken control of Petrus in London's Knightsbridge. Mr Hutcheson took advantage of the fact that Ramsay is not listed as a director or shareholder of the restaurant that they opened as a joint venture outside the main business. Ramsay is taking legal advice on the matter.

And the reason for the sudden split? That might be the £2m question. That, at any rate, is the amount for which Mr Hutcheson is suing Ramsay, slightly more than the £1.5m the former chief executive is rumoured to have taken from the business in personal loans. Although perfectly legal, the money was paid to Mr Hutcheson at a time when GRH was on the brink of financial ruin, somewhat incredibly for a business that used to turn over more than £100m a year. As Ramsay himself put it: "Jesus, where did that money go? I'm talking about pretty substantial figures. Into millions."

Unlikely as it seems for a Michelin-star-studded company that is even now just days away from one of London's most prestigious restaurant openings of the year – the Savoy Grill – GRH is in financial turmoil. Two years ago, the business almost went into administration after exceeding its £500,000 overdraft limit. It was later found to owe HM Revenue & Customs £7.2m in taxes. The company fell £4.3m into the red and last year its international arm, which includes sites in New York, Versailles and Tokyo, lost £8.3m.

Since then Ramsay, now represented by the PR Matthew Freud, has been pumping his own cash into GRH – more than £5m at the last count – money earned not from the sky-high cost of a meal at one of his establishments, but from his alternative career as a tyrannical TV chef. Although the latest viewing figures suggest that the British viewing public might be tiring of his infamous, expletive-ridden rants, with just over 1.5 million viewers tuning in for his latest Channel 4 series, Ramsay's Best Restaurants, the chef still has plenty of foodie fans in the US. Both Hell's Kitchen and Kitchen Nightmares are as popular as ever, netting him £300,000 per episode.

But not even the Americans will continue lapping up Ramsay indefinitely. With stories about the slow-motion car crash that is his personal life outstripping any critical acclaim for his restaurants – indeed, this year was the first for a decade that no Ramsay establishment made it into the influential Harden list of the 10 best places to eat in London – even his American star will start to wane.

Ironically, the success of his TV career is to blame for GRH's poor performance. Like a sous chef who took his eye off the soufflé, Ramsay diverted his attention from the restaurants that made his name. Not only did he barely have time to don a chef's hat in his own kitchens but, instead of cooking everything from scratch, some of his pubs served ready meals made en masse at a separate production site.

All of this has understandably knocked Tana Ramsay for six. She is used to her husband falling out with people – his former PR mentors Gary Farrow and Phil Hall, and numerous chefs, from Marco Pierre White and Jamie Oliver to Jason Atherton and Marcus Wareing, are all on the casualty list – but her family has always been safe. Until now.

Imagine how she must rue the publicity quote she gave to Children in Need: "I wouldn't be where I was today if it weren't for the constant support, love and care from my family. I can't imagine the pain of a child who hasn't been as lucky with their parents."

Just as she dared to hope things couldn't get any worse, up pops Sarah Symonds, her husband's alleged former mistress, this weekend with her own open letter. To Tana. Much as Gordon might love to hit the "off" button on his very public life right now, this is clearly one show that will run and run.